Jumping spiders may experience REM sleep

This little guy looks too Lively, no need for naps.

Our sleep takes a different brain The activity cycle is marked. Perhaps the most famous of these is REM or REM sleep, which is characterized by a loss of muscle control leading to convulsions and paralysis, and the eponymous eye movement. REM sleep is common in vertebrates, occurring in many mammals and birds; a similar period has been observed in lizards.

Figure out what could be beyond vertebrates however The research can be a little challenging because it’s not always clear what constitutes sleep, and many animals don’t move their eyes like vertebrates do. (For example, flies have to move their entire heads to reorient their eyes.) But an international team of researchers has discovered a group of jumping spiders that can reorient the inside of their eyes while they appear to be sleeping.

According to the team, spiders experience rapid eye movement sleep All characteristic eye movements associated with muscle twitches.

Spider Doze

Spiders, especially jumping spiders, may be more mentally active than assumed based on their small size and corresponding tiny nerves system. But the crux of the new study is that, apparently, they just need a nap sometimes. A year ago, some of the same team members were authors of a publication reporting on the spiders’ sleeping behavior. At night, they would find some overhanging vegetation, tie a thread to it so they could dangle over it, and stay there until the light returns in the morning. On the surface, they were sleeping.

This gives researchers the opportunity to avoid cross-species One of the bigger challenges in sleep research. The eyes of jumping spiders contain structures called retinal ducts, which can be moved to direct the spider’s vision to a specific location. These tubes are not visible in adult spiders due to the pigment in the spider cuticle. But newly hatched spiders take some time to develop the pigment, and they have translucent bodies that track the movement of retinal tubes.

So the researchers thought this was an excellent opportunity to see See if spiders might have REM-like phases when they rest at night. “The most striking indicator of REM sleep is eye movement during this phase,” they wrote. “However, mobile eyes have evolved in only a limited number of lineages — an adaptation that is conspicuously lacking in insects and most terrestrial arthropods — limiting cross-species comparisons.” For these jumping spiders, this limitation does not apply.

So, they turned off the lab lights , put the spiders into their sleep state, and then use an infrared camera to track any movements. Is REM a REM? ?

As you see in mammals, spiders undergo periodic rapid eye movements— — although movement of the retinal ducts is involved. Although these events vary by instance and individual, they generally last for a similar amount of time, and they repeat for a similar amount of time.

Perhaps more importantly, the movement of retinal tubes is often associated with spider legs of twitching or curling. Only about 40 percent of eye movement cycles are associated with leg twitches, but every leg twitch that occurs during sleep is associated with eye movements.

It is unclear whether this behavior represents REM, as it executes Same function as human REM sleep (we are still working to understand this). But physically, the signs seem to be there, which has some important implications. “These characteristic REM sleep-like behaviors exist in a highly visual, long-differentiated lineage, further challenging our understanding of this sleep state,” the researchers noted. Given that other researchers have published studies on cuttlefish and other distant This is especially true in the context of studies on REM-like behavior in allied animals.

But the spider in question here offers an obvious possibility to test the depth of similarity. It has been proposed that the eye movements of REM are a product of the replay of visual memories during sleep. In a laboratory setting, the spiders can be exposed to visual stimuli that force them to perform specific eye movement patterns. Afterwards, you can turn off the lights and see if the same pattern repeats during sleep.

PNAS, 2022. DOI: 10.1073/pnas .2204754119 (About DOI).